The present invention relates to an active radiation curable ink composition for inkjet recording, printed matter, a method of manufacturing printed matter, a molded article of printed matter, and a method of manufacturing a molded article of printed matter.
Various methods such as electrophotographic methods, sublimation-type thermal transfer methods, fusion-type thermal transfer methods, and inkjet methods are known as image recording methods in which images are formed on recording media, such as a paper, according to image data signals. For example, an inkjet method is an excellent image recording method because it can be carried out using inexpensive apparatus, it enables efficient use of ink and lower running costs since an image is directly formed on a recording medium by ejecting ink droplets only onto the region in which the image is to be formed, and it is less noisy.
The ink jetting method enables printing not only on a plain paper, but also non-water-absorbing recording media such as plastic sheets and metal plates. However, high speed printing and high quality images have been issues needed to be addressed, and the time periods required for drying and curing the ink droplets printed by the inkjet method significantly affect, for example, productivity of printed matter, sharpness of a printed image, and the like.
A recording method of using an active radiation curable ink composition for inkjet recording is known as one of ink jetting methods. According to the above recording method, the productivity of a print can be improved and a sharp mage can be formed by exposure to radiation immediately or in a finite period of time after injection of the ink, thereby curing ink droplets.
By increasing radiation sensitivity of the inkjet recording ink which can be cured by irradiation with radiation such as ultraviolet rays, a high curing property against the radiation is imparted to the ink, leading to various advantages such as improvement in productivity of inkjet recording, reduction in electrical consumption, longer life time of a radiation generator due to load reduction thereto, and prevention of evaporation of low-molecular-weight substances which may be caused by insufficient curing. In particular, by increasing the radiation sensitivity of the ink, the strength of an image formed from the inkjet recording ink is increased. However, the long-term storage stability of the ink is easily deteriorated, and it has been difficult to secure ejectionability (ejection property) at the time when the ink stored for a long period of time is ejected by ink-jetting.
In contrast, examples of preferable properties of images formed with ink include adhesiveness with a base material and flexibility of the image. In particular, the flexibility of the image becomes an important factor when the image is formed on the surface of an uneven (not flat) base material or a flexible base material, such or a resin film, or when a molded article of printed matte is manufactured such that a molded article is formed in a state where printing is performed on the surface, such as a resin bottle. However, it has been difficult to achieve a good balance between flexibility and curing properties. More specifically, there is a concern that an increase in the ratio of monofunctional monomers for improving flexibility causes reduction of the curing properties or stickiness of the image surface due to bleeding of uncured low molecular weight ingredients.
In order to improve adhesiveness, flexibility, and curing property, a technique in which a low-viscosity urethane acrylate is used in an inkjet ink composition has been suggested (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2002-167537).
In order to obtain a photopolymerization initiator composition which is cured at high sensitivity and has excellent storage stability, a technique is known in which a polyfunctional thiol compound having a specific structure is used as a component of a photopolymerization initiator composition for a photosensitive composition (see, for example, JP-A No. 2004-149755, or EP 1983017).
The present invention aims to address to the above problems.
More specifically, an object of the invention is to provide an active radiation curable ink composition for an inkjet recording suitable for an inkjet recording that has excellent ejection stability, high curing sensitivity, and further excellent stretchability of an image obtained by curing, a molded article of printed matter by using the active radiation curable ink composition for inkjet recording, and a method of manufacturing the same.